The President's Address. By Divkinfield H. Scott. 139 



have large, ovate, or oblong pinnules, somewhat cordate at the base, 

 and often attached to the rachis by a short stalk. The midrib is 

 distinct to near the end of the pinnule, where it breaks up into 

 small veins ; the angles between the veins are acute throughout. 

 The leaves are often much like those of an Osmunda, but in some 

 cases bear peculiar leaflets on the main rachis, differing from the 

 •ordinary pinnules. 



Alethoptcris, also a genus of very large, repeatedly-pinnate 

 fronds, is characterised by the broad decurrent base of the thick 

 oblong pinnules, the margins of which are strongly incurved 

 towards the lower surface. There is a midrib throughout, and the 

 angles between the veins are wide. There is a resemblance to 

 species of Pteris in some points, while the general appearance of the 

 enormous fronds may have been like that of Angiopteris, among the 

 Marattiaeese. 



Now in all these cases — and the same holds good for the many 

 other genera commonly considered as Ferns — there is no doubt as 

 to the thoroughly Fern-like nature of the fronds. That, however, 

 is not enough. There are some plants, even among Dicotyledons 

 of the present day, with foliage simulating that of Ferns, while in 

 the family of Cycads, which is more to the point here, there is 

 the often-quoted case of Stangeria, which, when first brought to 

 Europe from South-East Africa, was actually placed by botanists in 

 Lomaria, a well-known genus of Ferns,* until its cones appeared and 

 revealed its true nature. 



Other evidence than frond-characters had to be sought in order 

 to show what the Carboniferous " Ferns " really were. If we ask 

 what we mean botanically by a Fern, the answer must be, that above 

 everything else we mean a plant with a certain type of reproduction 

 and life-history. To take a common example : in the Male Fern, 

 familiar to everyone, we find that the asexual sporangia, containing 

 the spores, are borne in definite clusters, or sori, on the back of the 

 frond, and that each sporangium has a ring, or annulus, of enlarged 

 cells, by which its opening is effected when the spores are to be 

 shed. The spores germinate, under suitable conditions, and each 

 produces a small green organism, the prothallus, on which the 

 sexual organs are borne ; fertilisation takes place by means of the 

 actively swimming male cells, or spermatozoids, and an embryo is 

 the result, which grows up into a new Fern-plant, producing spores 

 in its turn — and so the cycle is completed. 



In the case of fossil plants we can rarely expect to find traces 

 of a delicate structure such as a Fern-prothallus, but we can and do 

 find evidence as to the nature of the sporangia. In a certain 

 number of the Carboniferous plants called Ferns the asexual organs 

 have been found, and have proved to be true Fern-fructifications. 



* Under the names Lomaria coriacea, L. erioput Kuntze, and L. lagopus T. Moore. 



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